Method of sizing paper pulp



Patented Apr. 8, 1930 JUDSON A. DE CEW, OF MOUNT VERNON,

OFFICE NEW YORK, 'AssIeNoa 'ro PROCESS ENGI- NEERS, INCL, NEW YORK, N. Y., A CORPORATION OF NEW YORK METHOD OF SIZING PAPER PULP No Drawing.

In the art of paper sizing there are many mysterious rea6tions'"that--takemplzm wli en brought together in water in the presence of paper making fibres. With the same quantity of size and alum being used there is no assurance that the same degree of sizing resistance will be obtained in the finished paper. This is due to the fact that sizingreactions must take place at a certain rate, which if exceeded a precipitate is formed that lacks the proper colloidal properties necessary to withstand the mechanical treatment that the stock receives.

There is another variable which influences the quality of sizing and that is whether the size is precipitated on the fibre surface or in the water surrounding the fibres. There are conditions under which it is desirable that the reaction between size and alum take place quickly in the solution carrying the paper.

stock, but this condition does not exist in beater sizing but in continuous sizing.

In beater sizing it is important that the reactions take'place slowly and that the size is coagulated on the fibreandmotin the solution.

In the present state of the art the control of the rate of sizing reactions is entirely experimental so that when aiformula is determined upon for a given condition it is maintained until inferior results demand a change in formulae. I

The common practice in sizing is to always add the size first to the paper stock and allow this to be dissolved and dispersed throu h the water in which the stock is moving efore adding thealum to the size and stock. When this is done the size is greatly diluted so that the rate of reaction between the alum and the size is retarded to such an extent that there is a. wide range of acidity that may be used, resulting from the use of different quantities of alum, without materially aifectin the final result. Even under these conditions a lar e excess of acidity may destroy the'colloida properties of the size before 1t reaches 7 I the paper machine.

If the conditions of sizing are reversed and the alum is addedto'the paper stock before Application filed May 24,

1929. Serial Ho. 365,?93.

the size and if the same proportionof the materials are used,

of .cases the sizing result will bedestroyed.

practice in mills that have a chemical check of these acidities, is to use suflicient alum after the size to give a pH. of about 4.5 in the solution. It is necessary to have this amount of acidity to complete the chemical reactions before the stock is used. s v

I have discovered that if I retard the rate of reaction by lower acidity, that I can obtain regular sizing results and produce a. great economy in the use of alum, by adding the alum first but using just a sufficient amount to' make the fibres astringent and have remaining in solution an acidity having a pH. of from lite 6.8. This acidity is lower-than generally used and, ispossible because in this condition the size reacts with the fibres.

The excess, acidityused will vary with the temperature of the stock, and'the time of the reaction, which is the time between theadding of the size and the use of the stock on the machine. The longer the time that the reaetiontakes place and the higher the temperature, the less the excess acidlty must be. The

the mostofit. Under certain conditions this M which is generallytwo parts I IOSlIl size and alum or sulphate of alumina are dfalum to one of size, then in the majority To give a specific example, the general.

stock can be sized when practically neutral water surrounds the fibres if they have previously absorbed a suflicient amount of alum.

The acidity of the water carrying the stock to be sized in this way must be very slight when a high free rosin size is used, and should be somewhere between 6 pH. and 7 pH., and

when a low free rosin acid as 5 pH.

The new principle involved in this process is that the small amount ,of alum used is near- 1y all absorbed by the fibres so that when the size solution is added a substantial part of the size is precipitated on the surface of the acidified fibre and the balance is slowly reacted upon by th'eslight amount of alum .remaining in solution. When the acidity is greater than a ove tat d; then the size is size is used it may be as be used as paper making ingredient.

coagulated by the alum solution and does not react with the astringent fibres.

I may go farther and wash out any free acidity in the water surrounding the pulp fibres or neutralize it, and then size the ulp by adding a diluted size to the acidified bres Eon that all of the size will be coagulated by the By means of this discovery I can size aper with a minimum of alum and size an thus obtain a paper with improved characteristics, as it is a well recognized fact that these two ingredients are both detrimental to the physica properties of the paper, such as strength, pliability, and durability.

In the use of my process disclosed in Patent No. 1,585,469, dated may 18th, 1926, in which I size the paper by the addition of size solution to the paper stockinthe Jordan engine after the'fibres'have been made astringeiifiwith alum, I find that the invention herein described contributes greatly to the eificiency of this process'but that with the new method the pa er can be sized without the rapid mixing 0 the Jordan, and the size may be added before the beater chest or at any other time after the alum treatment.

This process not only applied to the paper fibres but to any filling material that may If china clay is used this will have the capacity to ab-v sorb a considerable quantity of alum. If, therefore, this has the time along with the fibre to take up a large amount of alum and remove it from solution, then the clay can be sized in the same manner as the fibres, and a very small 'quantit of rosin -will size this material providing t e size reacts eventually with the clay and not with the solution.

While the size composition is usually referred to above as a solution, it is understood that it may include any kind of a saponaceous sizing composition dissolved in water, regardless of the concentration. a i

Having now described the invention what is claimed as new and for which Letters Patent of the United States is desired, is:

1. A method of 'sizin paper which consists first in making the fidires astringent with 'a solution of sulphate of alumina and having the solution surrounding the fibres at a pH.- of from 5. to 6.8, and lateradding a sizing material.

2. A method of sizing paper which consists in first making the fibres astringent with a solution of sulphate and'having a pH. of from 6 to 6,8 and then adding a solution of free rosin size.

3. A method of sizing aper which consists in treating the paper ma 'ng fibres with sulphate of alumina, allowin the fibres to absorb the alum until the p of the solution is over 5, and then treating thesurface of the astringent fibres with a solution of rosin size.

4. A step in the method of sizing paper which consists in treating an acidified fibre with a solution of rosin size.

5. A method of sizing paper which consists in making the fibres acid in character, then removing any acidity in the solution, and then adding a solution of sizing material.

6. A method of sizing paper which consists in treating the fibres with a sulphate of alumina solution until the fibres have absorbed more than one-half of the alum, leaving a pH. in the solution of over 5, and then treating the fibres with a sizing composition.

7. A step in the method of sizing pulp which consists in coagulating a rosin size on the surface of an acidified fibre.

8. A method of sizing paper stock consisting of fibrous and filling material, which consists in making all of the material astringent from the absorbtion of sulphate of alumina and leaving remaining in solution just enough acidity to give a pH. of from 5 to 7 and then treating the material with a sizing solution.

9. A method of sizing paper making fibres which consists in treating the fibres with a solution of sulphate of alumina in such a manner that when a size solution is added to the paper stock in the beater the size will react with the fibres more rapidly then it will with the solution.

10. A method of sizing paper making fibres which consists in treating the fibres with a solution of sulphate of alumina in such a manner that when a size is added to the paper stock chest, the size will react with the fibres more rapidly than it will with the solution.

11. A method of sizing paper making fibres which consists in treating the fibres with a solution of sulphate of alumina in such a manner that when a size solution is added in a mixing device between the heater and the Jordan the size will react with the fibres more rapidly than it will withthe solution.

Signed at New York, in the County of New York and State of New York,-this 22nd day of May, 1929;

JUDSON A. DE CEW. 

